Branch Chain Variations Modulate Pyridine Derivative Adsorption for Long‐Life Zinc‐Ion Battery

Abstract Aqueous zinc‐ion batteries (AZIBs), candidates for large‐scale energy storage, face limitations due to the poor reversibility of zinc anodes. It reports on pyridine derivatives with high donor characteristics, including 2‐chloro‐1‐methylpyridinium iodide (CMPI) and pyridine‐2‐acetaldoxime methyl iodide (PAMI), as effective additives. At lower concentrations, these additives markedly curtail the zinc dendrites formation and the evolution of hydrogen on the zinc anode, thereby prolonging the AZIBs life. Through a combination of theory and experiments, the impact of side‐chain groups on the kinetic process of zinc depositioni is elucidated. In contrast to PAM⁺, CMPI⁺ demonstrates enhanced adsorption and self‐assembles at the anode‐electrolyte interface, forming a barrier to free water and a protective ZnI layer via I⁻ ion integration. This dual‐layer strategy boosts zinc plating/stripping reversibility by 100‐fold and achieves a coulombic efficiency of 99.7% in zinc–copper half‐ batteries. The findings advance the understanding of electrolyte additive structures on zinc deposition, providing a molecular framework for screening additives in aqueous metal‐ion batteries.